Method of plating metal uniformly on and throughout porous structures

ABSTRACT

A method of uniformly coating ceramic and alumina porous structures such as honeycomb and sponge structures are disclosed. The method comprises radiantly heating a rotating workpiece until the temperature of the workpiece reaches the decomposition temperature of a thermally decomposable metal bearing gas. Passing a metal bearing gas over the structure whereby a uniform and firmly adhered coating is obtained on and throughout the workpiece.

United States Patent Clyde Aug. 19, 1975 [54] METHOD PLATING METAL3,121,925 2/1964 Toulmin 1 17/1072 R X UNIFORMLY ON AND THROUGHOUT3,158,499 1 H1964 .lenkin i 117/1072 R 3,160,517 12/1964 Jenkin 118/495X 3,213,827 10/1965 Jenkin 1 18/495 Inventor: Robert A. Clyde, 165Burlington Ave., Rochester, N.Y. 14619 Filed: Feb. 21, 1973 Appl. No.:334,261

Primary Examiner-Leon D. Rosdol Assistant Exam inerl-larris A. PitlickAttorney, Agent, or FirmDenson and Kurtzman [5 7] ABSTRACT A methodofuniformly coating ceramic and alumina porous structures such ashoneycomb and sponge structures are disclosed. The method comprisesradiantly heating a rotating workpiece until the temperature of theworkpiece reaches the decomposition temperature of'a thermallydecomposable metal bearing gas. Passing a metal bearing gas over thestructure whereby a uniform and firmly adhered coating is obtained onand throughout the workpiece.

8 -Claims, 4 Drawing Figures PATENTEI] AUG] 91975 SEIZU 1 SF 2 PATENTEDAUG 1 9 I975 say-:51 2 OF 2 METHOD OF PLATING METAL UNIFORMLY ON ANDTHROUGHOUT POROUS STRUCTURES FIELD OF THE INVENTION This inventionrelates to a method of metallizing porous ceramic and alumina structureswherein the metal is plated onto and throughout the structure in auniform manner. The invention further relates to the products obtainedfrom the method of coating and their uses.

DESCRIPTION OF THE PRIOR ART There have been a number of methodsdescribed for coating alumina and ceramic structures with metals. Amongthe more prevalent methods are solution deposition of metals ontoalumina or ceramic structures and vapor deposition or gas plating ofmetals on alumina and ceramic structures. The metal plated structuresare more popularly employed as catalysts and in heat exchange systems.

The various methods of solution deposition described in the prior arthave several disadvantages over the vapor deposition of metals ontoalumina and ceramic substrates. Solution deposition is expensive sincevery often the water soluble or water insoluble salts employed can becostly and the equipment employed is expensive. Quite frequently, themethods employed result in the production of noxious and corrosivecompounds such as nitrogen compounds, should the soluble salts employedbe in the form of nitrates, and means must be provided for handling thenoxious gasses. The methods most often require multiple impregnationsand hence therefore require multiple dryings. The purity of the platingof metals is difficult to control since very often contaminating ionsare introduced which must be removed either by calcination or washingprocedures.

In any event, the technique of solution deposition results in a productwherein the plated metal is generally not firmly adhered to thesubstrate and flaking readily occurs under high temperatures and severeuse. Flaking or breakage can result in the producing of fines which clogpacked towers and cause undesirable pressure drops. Should a platedcatalyst be employed in an auto muffler, fines can cause back pressureand a drop in engine efficiency. A significant advantage of vapordeposition over solution deposition is that one may obtain asubstantially pure metal plate upon a ceramic structure (hereinafter theterm ceramic will be understood to include alumina, silicon carbide,silicon dioxide as well as other ceramic materials) which plate stronglyadheres to the substrate under high temperatures and severe conditions.

The use of metal plated ceramic sponge or honeycomb structures ascatalysts is often more desirable than metal plated ceramic pellets orspheres. With spheres, or pellets, there is an inefficient heat transferdue to the resistance in point to point contact of the particles. As aresult of the inefficient heat transfer, there is a loss in thecatalytic activity of the materials due to sintering poisoning andflaking. On the other hand, resistance to heat flow is low with respectto sponge or honeycomb structures, heat can readily be removed from orpassed into a sponge or honeycomb catalyst more simply. The lowresistance to heat flow results in a desirable catalyst for endothermicreactions such as reforming and the production of inert gasses and forexothermic reactions such as methanation. Due to enlarged void spacesand resultant lowpressure drop and high through put, the honeycomb andsponge structures are more efficient as a catalyst and due to the lowerweight of the structures as compared to pellets and spheres there isless stress on any supporting plate in a packed column or otherwise. r

In US. Pat. No. 3,075,494 of Toulman, Jr., issued Jan. 29, 1963, thereis disclosed an apparatus and method for making metallized porousrefractory material. In order to obtain a uniform plate of the metal onand throughout a sponge or honeycomb workpiece, the temperature of theworkpiece must be uniform throughout. Since ceramics are insulators, itis readily understandable that a temperature gradiant will necessarilyoccur across honeycomb and sponge structures unless all portions of theworkpiece are uniformly heated. By maintaining the structure in a rigidposition as disclosed by Toulman, Jr., the middle, front and backs ofthe workpieces are heated by convection and thus would not be at thesame temperatures as other portions of the material. The temperaturegradiant across the material will necessarily result in a nonuniformdeposition of the metal since the metal bearing gas decomposes slower atthe lower temperatures.

US. Pat. No. 3,160,517 of Jenkin, issued Dec. 8, 1964, attempts toovercome the problem of nonuniform deposition of the coating on porousstructures. v

In accordance with the described technique infared heat rays aredirected onto one side only of the porous body while forcing the metalbearing gasses through the porous body from one side to the other side.This use of forced gas and heating from only one side again results innon-uniform deposition as a result of temperature gradients within thestructure.

It is readily understood that a significant advance in the art would beobtained by a process which would allow for the uniform deposition ofmetal upon a ceramic honeycomb or sponge structure. The improvementwould be even more desirable if the techniques and apparatus employedare simple as compared to the prior art.

SUMMARY OF THE INVENTION This invention eliminates the majordisadvantages of the prior art metal deposition processes in that it hasbeen unexpectedly discovered that a honeycomb or sponge ceramicworkpiece can be subjected to gas deposition of a metal in a manner suchthat the metal can be deposited uniformly on and throughout thestructure in a simple manner.

The process for uniformly plating a metal by 'vapor deposition on andthroughout a substrate or workpiece which has a structure of a honeycombor sponge comprises heating in an enclosure, a rotatably suspendedworkpiece or substrate by radiant means until the substrate reaches thetemperature of a thermally decomposable metal bearing gaseous compound,rotating the substrate and passing a thermally decomposable metalbearing compound into the enclosure along with a carrier gas in a mannersuch that the gas comes into intimate contact with the substrate-whilecontinuously r0- tating the substrate whereby the metal is uniformlyplated on and throughout the substrate.

In accordance with the invention there is further obtained a ceramichoneycomb structure having the longitudinal axes of all its cellsparallel to each other, the

improvement comprising a uniform coating on and throughout the structuresaid coating being firmly adhered to the ceramic substrate. Theinvention further provides ceramic sponge structures having uniformlycoated on and throughout said structures or substrates a firmly adheredmetal plate.

It is therefore an object of this invention to provide a process foruniformly plating a metal on and throughout ceramic honeycombs.

It is another object of this invention to provide a process foruniformly plating a metal on and throughout a ceramic sponge.

It is still another object of this invention to provide an improvedprocess for the vapor deposition of a metal uniformly on and throughouta ceramic honeycomb or sponge.

Still another object of this invention is to provide a method forplating a ceramic honeycomb or sponge with a metal in an economic andsimple manner.

Yet another object of this invention is to provide a ceramic honeycombor sponge structures plated uniformly on and throughout the structurewith a metal.

Still yet another object of this invention is to provide a ceramichoneycomb or sponge structure having a pure and uniform metal plate onand throughout the structure.

A further object of the invention is to provide ceramic honeycomb andsponge structures having a firmly adhered to plate of a pure metal.

A further object of the invention is to provide ceramic structureshaving a plate of a major amount of one metal and a minor amount of atleast one other metal.

Still yet another object of this invention is to provide metal platedceramic honeycombs or sponges which are useful as catalysts and in heatexchange systems.

These and other objects of this invention will be understood from thedescription and drawings and the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the enclosure whichmay be employed in gas plating ceramic objects in accordance with thisinvention.

FIG. 2 is a perspective view of a ceramic honeycomb structure.

FIG. 3 is a perspective view of a ceramic sponge which may be plated inaccordance with this invention.

FIG. 4 illustrates the gas plating apparatus for carrying out the metalplating ceramic honeycombs and sponges.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings inmore detail, FIG. 1 depicts the enclosure which can typically beemployed in the gas plating operation. The apparatus comprises theoverall assembly 1 having a top metal panel 2 and a bottom panel 4.Typically the top and bottom panels are made of steel. Attached to thepanels are cooling lines which can be spot welded to the steel. Thefront panel 3 has a glass window 8 for observation purposes andadditionally contains cooling tubes 10. The side panels 5 and 7 containteflon window panels 9. The apparatus further comprises gas inletconduits 11 and gas outlet conduits 12.

FIG. 2 illustrates a honeycomb 13 having parallel cells 14.

FIG. 3 illustrates a sponge 15 with random cells and passages 16.

FIG. 4 illustrates a coating method and operation. The workpiece 13 tobe coated is suspended from a suspension member arm 18 that holds theworkpiece. The suspension member 18 is on a rotating base 19 therebypermitting the workpiece to be continuously rotated during the gasplating operation. The gas spray 17 enters the enclosure through a gasspraying device 23 while the workpiece 13 is continuously rotated.During the coating operation the workpiece is radiantly heated by a bankof infrared tubes 24 located at the sides of the enclosure. The unusedgas and carrier gases pass through the outlet tube 12 through a trap 20burning station 21 and finally exhaust through 22.

In accordance with this invention, it has been unexpectedly andunobviously discovered that by rotating the workpiece having paralleland non-parallel passageways therein, while radiantly heating theworkpiece there is essentially no temperature gradiant across theworkpiece. It is because of the uniform temperature throughout theworkpiece i.e. in the middle as well as on the outsides that one obtainsa uniform plate of metal on and throughout the workpiece.

Generally, rotation about a single axis is sufficient. With respect tolarge workpieces or workpieces having odd shapes various portions of theoutside, for example, the top and bottom, may not be in line with thedirect rays of the heating lamp and therefore not properly radiantlyheated. The workpiece can then be alternatively rotated about an axisnormal to the original axis of rotation or the workpiece can merely bealternatively angled so as to bring all portions of the piece into thedirect ray of the lamp. With very large workpieces, it can be extremelydifficult to rotate about 360 and hence it is desirable to oscillate thepiece through an angle of about 30 in order to obtain uniformtemperature across the piece.

The ceramic honeycombs and sponges and their methods of preparation arewell known in the art and need no extensive description herein. US. Pat.No. 3,502,596 of Sowards adequately describes ceramic structures andcites a number of patents describing methods for preparing ceramichoneycombs. Other patents disclosing ceramic structures are U.S.- Pat.Nos. 3,378,431 of Crandall and 3,090,094 of Schwartzwalder. Crandall,Schwartzwalder and Sowards are hereby incorporated by reference.

The sponges are made in a simple manner, for example, a paste mixturecomprising 85.7% water, 10% aluminum hydroxide [Al(OI-I) 3.5% of asurfactant (CF-54 from Rohm and Hass) and 0.8% ofa 35% solution ofhydrochloric acid is prepared. A polyvinyl acetate sponge or a spongemade of similar materials such as nylon is soaked in the mixture. Thesponge and paste mixture is heated slowly especially through the rangeof 300 to 350 Centigrade where the sponge material, if acetate,decomposes. The remains are slowly heated to 1,000C. and thereafterslowly cooled, whereby one obtains a ceramic or alumina sponge. The May1967 issue of Ceramics Industry describes the preparation of foam usingalbumin.

The ceramic honeycombs or sponge materials are readily obtainable on acommercial basis from companies such as Champion Spark Plug Company,Detroit,

Mich.; American Lava Company, Chattanooga, Tenn.; Hexcel Company ofDublin, Calif; Scott Paper Company of Eddystone, Pa. and Corning GlassCompany of Coming, N.Y.

While it is generally desirable to obtain a workpiece with a pure plateof metal such as nickel, often it is desirable to have a minor portionof a second metal incorporated in with the plate such as platinum,cobalt, ruthenium or copper. Ruthenium for example can be put onto anickel coated sponge electrolytically. Such a nickel plated spongehaving minor amounts of ruthenium plated thereon acts as an excellentmethanation catalyst since minor amounts of ruthenium trigger anexothermic reaction which would enable the nickel to carry on as acatalyst and at the same time the nickel sponge with its heat exchangecapabilities enables and helps to remove the heat. Rare earthcompositions are plated with great difficulty upon ceramics but with ametal plate upon the ceramics, the coating of an adherable rare earthcomposition, such as for example, lanthanum lead manganite is greatlysimplified.

A method of adding platinum to the nickel plate would be to place anamount of platinum acetonyl acetonate in the nickel carbonyl line orsmall amount of the acetonate can be dissolved in nickel carbonyl. Othermethods of incorporating minor or major amounts of other metals such aspalladium, copper and cobalt are well known in the art and would beobvious to those of ordinary skill in the art.

The honeycomb or sponge structures can comprise virtually any ceramicmaterial, for example, these materials could include boro-silicates,soda-lime-silicates, lead silicates, alumino-silicates and alkalineearth silicates; sillimanite magnesium silicate, magnesia, zircon,zirconia, petalite, spodumene, cordierite, corundum, glass ceramics,beryllium oxide and zirconium oxide. In accordance with a preferredembodiment, it is desirable to use as ceramic materials lithium aluminumsilicate, alumina and silicon carbide.

The typical plating chamber comprises a rectangular shaped enclosurehaving a glass front window and ten mil thick FEP teflon tightlystretched. The tops, bottoms and the backs can be made from steel andare cooled with copper tubes containing cooling liquid. In a typicaloperation for plating small ceramic workpieces, the chamber would be l0inches wide, inches high and 16 inches deep. However, size of theplating chamber necessarily depends on the size of the piece to beplated. The sides and fronts are cooled either by air fans or a waterspray in order to prevent plating of the metal upon the insides of theenclosure. On both sides of the enclosure are located banks of 17 inchlong infared lights and reflectors, the number of lights employed ofcourse is a function of the decomposition temperature of the metalcontaining gas as well as the size of the workpiece and other factorswhich are obvious to those of ordinary skill in the art. Round lightscan also be employed in place of the light tubes.

In a typical method of plating a workpiece, the workpiece is cleaned inorder to remove the grease and fingerprints. The workpiece is placedonto a rotatable suspension means and the airtight chamber is closed.The chamber is then purged with nitrogen gas at about 9.8 cubic feet perhour and shortly thereafter the lights are turned on. It is importantthat the heating lamps be on for no more than 40 seconds in order toavoid overheating the teflon windows. Typically, lights would beactivated for about 20 to 30 seconds and deactivated for about 20 to 30seconds. After purging with nitrogen, the chamber is then purged withcarbon monoxide for approximately a half an hour. The carbon monoxidenot only helps to purge the chamber of air but also helps to activatethe surface of the workpiece. The chamber will have a small metal tab inclose vicinity to the workpiece and connected with a thermocouple. Assoon as the temperature of the workpiece reaches the decompositiontemperature of a metal bearing gas the metal bearing "gas is allowed toflow in through the chamber at a rate of about 0.3cc/minute. The metalbearing gas will typically go through a vaporizer and then mix with thecarrier gas which is typically carbon monoxide and then allowed to flowinto the chamber. Plating should begin in about 15 minutes. However, ifplating does not begin, 3cc of H 8 gas should be passed into the chamberto help initiate the plating process. Hydrogen sulfide should not beemployed however if it will interfere with subsequent catalytic uses ofthe product. After about an hour, the workpiece will be uniformly coatedand the chamber purged and allowed to cool.

In carrying out the gas plating, one may employ any of theknown-'heat-decomposable gaseous metal carbonyls.

Illustrative compounds are the carbonyl types such as for example,nickel, copper, iron or chromium carbonyls and mixed carbonyls of thesemetals. Other types of heat decomposable compounds are metal nitroxyls,nitrosyl carbonyls; hydrides and metal alkyls such as magnesium diethyl.Further useful gaseous metal compounds are the carbonyl halogens, forexample, osmium carbonyl bromide, ruthenium carbonyl chloride, and thelike.

The decomposition temperature of the heatdecomposable gaseous metalcompound will control the temperature to which the workpiece is brought.For example, nickel carbonyl will decompose at a favorable rate for thisprocess at about 350 to about 450F. Accordingly, the metal bearing gasis passed into the enclosure when the temperature of the workpiece isfrom about 350 to about 450F and preferably from about 410F to about450F. In a preferred aspect, the metal bearing gas is passed into theenclosure when the workpiece is at a temperature of about 410F.

In a typical operation, the workpiece is rotated at a rate of about tworotations per minute (rpm) to about 20 rpm. However, higher rates ofrotation may be employed when so necessary. In a preferred embodiment,the rate of rotation is at about five rpm to about 10 rpm. In anotherpreferred embodiment, the rate of rotation is seven rpm.

The thickness of the plate is determined by its use. In accordance withthis process, the plating can be from about 0.1 mils-to about 500 mils.

A significant advantage of our process over prior art processes of metalplating onto ceramic porous structures is its speed. Additionally, athicker plate can be obtained which plate is uniform. Thus, if catalystpoisoning occurs during subsequent use, the outer metal layers can bereadily removed such as by dipping in acid and reactivation of thecatalyst is obtained.

EXAMPLES The following examples are included for a further understandingof the invention.

Example I An alumina sponge structure, obtained from Champion Spark PlugCompany of Toledo, Ohio, having the approximate dimensions of 2 X 2 X /2inches is rotably suspended in an airtight chamber. Outside and to thesides of the chamber are located 17 inch long IR lamps with reflectors(three on each side). The lamps are continuously activated anddeactivated at a rate so as to prevent the melting of the teflon sidesof the chamber but gradually causing an increase in the temperature, asmeasured by the temperature of the tab next to the workpiece. Thechamber is purged for approximately 1.5 hours with nitrogen followedwith purging mixture comprising a minor amount of nitrogen with carbonmonoxide. The workpiece is heated to a temperature of 410F, whichtemperature is maintained throughout the plating operation. Rotation ofthe suspended structure at the rate of seven rpm is initiated andvaporized nickel carbonyl in carbon monoxide carrier gas is passed intothe chamber. At the end of 1 hour there was obtained a medium uniformcoating of nickel on and throughout the structure and which firmlyadhered to the structure.

Example 2 An alumina sponge structure having the dimension of 2 X 2 X /2inches was treated in the same manner as in Example 1 however the timeof exposure of the sponge to the plating gas was reduced to 40 minutes.On close examination of the structure, there was observed a uniform thinand firmly adhered coating of nickel on and throughout the structure.

Example 3 An alumina sponge structure as in Example 1 was treated in thesame manner as in said Example with the exception that the structure wasexposed to the plating gas for 1 hour. At the end of 1 hour, thestructure had a uniform heavy coating of nickel of approximately 1.5mils thickness which was firmly plated onto the structure.

Example 4 An alumina sponge structure in the shape of a cylinder 3inches high and 4 inches in diameter is suspended so that itslongitudinal axis is horizontal and can be rotated about an axisperpendicular to the horizontal axis. The alumina structure weighed139.99 gms prior to treatment. The sample is treated in the same manneras in Example 1 except that the structure was exposed to the plating gasfor 2 hours and 44 minutes, with the temperature gradually increasing to450F for the first 1.5 hours and maintained at 450F thereafter. Thesample was observed to have a uniform coating of nickel on andthroughout the structure which firmly adhered to the alumina. The sampleafter treatment weighed 183.10 g.

Example 5 A lithium aluminum silicate honeycomb structure having cellsapproximately /a inch in diameter and the dimensions of 1% X 4% X /2inches is suspended in an airtight chamber in a manner such that thelongitudinal axis of the honeycomb cells are horizontal and the piececan be rotated about the axis perpendicular to the horizontal axis. Thechamber is purged for 1 hour and 10 minutes first with nitrogen and forthe final l0 minutes with a mixture of nitrogen and carbon monoxide. TheIR lamps are continuously alternatively activated for 37 seconds anddeactivated 25 seconds in order to bring the temperature to 435F asmeasured by the temperature of the tab placed next to it. The lights arethen activated and deactivated so as to maintain the 435F temperaturethroughout the operation. Upon completion of the purge operation, thesample is continuously rotated at seven rpm while passing in vaporizednickel carbonyl in carbon monoxide and nitrogen carrier gasses. At theend of 1 hour an approximate 3.5 mil coating of nickel was uniformlyplated on and throughout the honeycomb.

Example 6 A ceramic honeycomb having the dimensions as the honeycomb inExample 5 is treated in the same manner as in Example 5. The ceramichoneycomb was uniformly plated throughout the structure with nickel.

Example 7 A silicon carbide workpiece is treated in the same manner ofExample l. A uniform plate of nickel was obtained on and throughout theworkpiece.

Examples 8-1 1 Four separate silicon carbide workpieces maintained at410F and rotating at seven rpm are separately exposed, in an airtightenclosure, to nickel carbonyl in carbon monoxide carrier gas. Eachsample is exposed for 15 minutes. Each workpiece was coated with a 4.5mil thick uniform plate of nickel throughout the piece.

Example 12 Example 13 Measurement of Heat Conductivity Two 1% inchcolumns, one packed with nickel coated sponge pieces of this invention,the second packed with inch nickel coated saddles were placed on a standsitting on a hot plate. Surrounding each column is 250 ml H O. The rateof transfer of heat from the hot plate through the packed columns to theH 0 was measured by measuring the temperature of the water at timedintervals. The results of the test is summarized in Table l. The resultsshow the sponge pieces transfer heat to the water appreciably fasterthan the saddles.

TABLE I Timc TC H O Around Saddles TC H O Around Sponge TABLEI-Continued The metal plated honeycombs and structures can be usefullyemployed as an efficient heat exchange material with or withoutcatalytic activity. With spheres or pellets there is an inefficienttransfer of heat due to the resistance in the point to point contacts ofthe particles. On the other hand, a monolithic structure with randomholes transfers heat in several directions without the narrowrestriction of the point to point contact and thereby heat can bereadily transferred to a pipe wall or flat plate and thereafter removedby a fluid which is located on the other side of the wall area. The useas a heat exchanger therefore would cause the monolithic structures tobe useful in exothermic reactions such as in methanation of coal gas.The metal plated monoliths when employed as a catalyst will not sufferas a result of sintering, poisoning and flaking as a result of thefailure to transfer heat and therefore can be usefully employed not onlyas an efficient heat exchanger but as a catalyst such as in the watergas shift reaction (CO-l-Steam H +CO Additionally, due to the lowresistance of the heat flow, heat can be passed to the catalyst readilyfrom the outside of a barrier such as apipe or flat piece in order toencourage endothermic reactions such as reforming reactions and inreducing atmospheric generators.

When packed in packing columns, the catalyst produce less stress on thesupport plates because of the large void spaces and as a result of thelarge void spaces there is a resultant low pressure drop with a highthroughput with respect to gasses.

Other typical exothermic reactions in which the metal plated porousmonoliths are useful are in hydrogenations, chlorinations andoxychlorinations.

Because of the excellent heat removal abilities of the honeycombs andsponges, they may be readily employed in rotary kilns to recover asubstantial amount of the heat which is normally passed to theatmosphere. The heat exchanger employing the metal coated ceramics canreadily recover the waste heat. The waste heat could then be employed topreheat the incoming air. Ordinary heat exchanges are inefficientbecause the heat transfer coefficient on the gas side is low. Byincreasing the area on the gas side with a honeycomb or sponge, the heattransfer can be markedly improved. The hot gasses are transferred fromthe metal coated sponge to the flat plate or tube and thereafter to thecold material on the other side of the plate or tube. Air pollution fromthe kiln would also be reduced by the catalyst action of the nickel.

In the methanation of coal gas, nickel is an ideal catalyst. Thecatalytic activity accompanied by the heat transfer as a result of theuse of nickel plated sponges would significantly improve methanation ofcoal gas. Low pressure drop would make it very useful in the hot gasrecycle line.

A most important use with respect to metal plated ceramics such asnickel plated honeycombs and sponges with or without a small amount ofplatinum would be in auto emmission controls.

Pellets tend to abraid each other thereby grinding off the activecatalyst whereas the abraiding would be avoided through the use ofsponges or honeycombs. The resultant improvements obtained with respectto this process in plating sponges and honeycombs uniformly throughoutand on the structures with metal such as nickel causes the structures tobe highly desirable in catalytic converters for auto emmission control.The structures can also be usefully employed in the Stirling AutomotiveEngines. The Stirling is a closedcycle engine which employs a light gassuch as hydrogen or helium as a working fluid. The gas is first heatedand then expanded and cooled in order to obtain energy. Since metalplated particles of this invention act as an excellent heat transferagent as well as a catalyst, these materials would be highly useful asregenerators in Stirling Engines or recuperators in stationary units.

The invention has been described in detail with par ticular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

1 claim:

1. A process for uniformly plating metal by vapor deposition on andthroughout one of a ceramic or alumina substrate having the structure ofone of a honeycomb or sponge, the process comprising heating in anenclosure a rotatably suspended substrate by radiant means until thesubstrate reaches the decomposition temperature of a thermallydecomposable metal bearing gaseous compound, rotating the substrate,passing a thermally decomposable metal bearing compound into theenclosure along with a carrier gas so as to have the gas come intointimate contact with the substrate while continuously rotating thesubstrate at a rate of at least about two rpm and continuouslyactivating and deactivating the radiant means so as to maintain thetemperature of the workpiece at about the decomposition temperature ofthe metal bearing gas, whereby the metal is uniformly plated on andthroughout the substrate.

2. The process of claim 1 wherein the honeycomb or sponge substrate isone of A1203. LiAlSiO or SiC.

3. The process of claim 1 wherein the metal bearing gaseous compound isnickel carbonyl.

4. The process of claim 3 wherein the substrate is heated to at leastfrom 3 10F to about 450F.

5. The process of claim 1 wherein the substrate is rotated at the rateof from about two to about 20 rpm.

6. The process of claim 5 wherein the substrate is rotated at the rateof about seven rpm.

7. The process of claim 1 wherein the substrate is oscillated through anangle of about 30.

8. A process for uniformly plating nickel on and throughout an aluminaor ceramic sponge or honeycomb substrate, comprising:

a. radiantly heating in a nitrogen and carbon monoxide purged airtightchamber the rotatably suspended substrate to from about 340F to about450F;

b. continuously rotating the substrate at a rate of about 7 rpm;

c. continuously activating and deactivating the radiant means so as tomaintain the temperature;

(1. while rotating and activating and deactivating the radiant meanspassing vaporized nickel carbonyl into the chamber so as to come intointimate contact with the substrate whereby nickel is uniformly platedon and throughout the substrate; and

e. removing the plated substrate from the chamber.

1. A PROCESS FOR UNIFORMLY PLATING METAL BY VAPOR DEPOSITION ON ATHROUGHOUT ONE OF A CERMIC OR ALUMINA SUBSTRATE HAVING THE STRUCTURE OFONE OF A HONEYCOMB OR SPONGE THE PROCESS COMPRISING HEATING IN ANENCLOSURE A ROTATABLY SUSPENDED SUBSTRATE BY RADIANT MEANS UNTIL THESUBSTRATE REACHES THE COMPOSITION TEMPERATURE OF A THERMALLYDECOMPOSABLE METAL BEARING GASEOUS COMPOUND, ROTATING THE SUBSTRATE,PASSIN A TEMNINALLY DECOMPASABLE METAL BEARING COMPOUND INTO THEENCLOSURE ALONG WITH A CARRIER GAS SO AS TO HAVE THE GAS COME INTOINTIMATE CONTACT WITH THE SUBSTRATE WHILE CONTINUOUSLY ROTATING THESUBSTRATE AT A RATE OF AT LEAST ABOUT TWO RMP AND CONTINUOUSLYACTIVATING AND DEACTIVATING THE RADIANT MEANS SO AS TO MAINTAIN THETEMPERATURE OF THE WORKPIECE AT ABOUT THE DECOMPOSITION TEMPERATURE OFTHE METAL BEARING GAS, WHEREBY THE METAL IS UNIFORMLY PLATED ON ANDTHROUGHOUT THE SUBSTRATE.
 2. The process of claim 1 wherein thehoneycomb or sponge substrate is one of Al2O3. LiAlSiO4 or SiC.
 3. Theprocess of claim 1 wherein the metal bearing gaseous compound is nickelcarbonyl.
 4. The process of claim 3 wherein the substrate is heated toat least from 310*F to about 450*F.
 5. The process of claim 1 whereinthe substrate is rotated at the rate of from about two to about 20 rpm.6. The process of claim 5 wherein the substrate is rotated at the rateof about seven rpm.
 7. The process of claim 1 wherein the substrate isoscillated through an angle of about 30*.
 8. A process for uniformlyplating nickel on and throughout an alumina or ceramic sponge orhoneycomb substrate, comprising: a. radiantly heating in a nitrogen andcarbon monoxide purged airtight chamber the rotatably suspendedsubstrate to from about 340*F to about 450*F; b. continuously rotatingthe substrate at a rate of about 7 rpm; c. continuously activating anddeactivating the radiant means so as to maintain the temperature; d.while rotating and activating and deactivating the radiant means passingvaporized nickel carbonyl into the chamber so as to come into intimatecontact with the substrate whereby nickel is uniformly plated on andthroughout the substrate; and e. removing the plated substrate from thechamber.